Self-propelled or stationary construction machines having rotating work devices or work tools for processing soil surfaces or for chopping material are known from the prior art. A schematic side view of such a construction machine is shown in FIG. 1. The construction machine 10 has a machine frame 60 and a drive source 70 for the drive of transport units 20. Furthermore, the construction machine 10 is equipped with work devices 30, of which only a milling roller for milling the soil surface 40 is shown. The milling roller 30 is driven by a roller drive, which can be decoupled from the milling roller 30. The roller drive is performed by means of the drive source 70, which also drives the transport unit 20, or by means of a separate drive source. The milling roller 30 can be displaced, for example, by using hydraulic cylinders 50, into a raised position, i.e., into an idle position, when the milling roller 30 is not in milling operation. The milling rotor is not engaged with the soil in the idle position.
In operation of the milling roller 30, the force flow is transmitted by means of a switchable clutch, which is optionally implemented with or without a decoupling element, to a belt drive, and fed from the belt drive to the milling roller. For this purpose, a reduction gearing is positioned between the belt drive and the milling roller or between the drive source and the switchable clutch. The switchable clutch can be actuated hydraulically, electrically, pneumatically, mechanically, or in another manner. The switchable clutch can be an elastic clutch, for example.
Engaging the milling roller 30 requires a defined sequence. Firstly, the first drive source must be brought to a reduced speed, typically to the idle speed, before the engagement procedure of the milling roller 30 can be performed. Subsequent to this, the drive source speed of the first drive source can be increased again, so that the desired operating speed of the milling roller 30 is reached. The engagement procedure is designed in such a manner that the entire drive train must be accelerated and synchronized in slip operation of the clutch and the belt drive.
There are comparable concepts in the field of self-propelled agricultural machines with equipment such as field choppers for chopping plant products.
The known concepts for driving a rotating work device of construction machines or agricultural machines have the disadvantage that the switchable clutch and the belt drive are subjected to increased wear, which is largely caused by the required engagement procedure and the slip operation. The clutch can only be shifted at low speeds or speed differences. During the engagement procedure, the drivetrain runs for a certain time in slip operation, which is lengthened still more as a function of the speed difference and the mass inertias of the drivetrain. This results in shortening of the service life of the components.
It is not possible to engage the milling roller drive unit or the work device when the drive source is shut down.
In addition, the switchable clutches used are costly, since they must be specially produced for specific machines in small quantities. Furthermore, it is a disadvantage that such a switchable clutch and a belt drive require a relatively large space.
A self-propelled construction machine having a work device, in particular, a work roller, for carrying out work required during construction measures is known from DE 10 2007 019 202 A1, the construction machine having a drive device having two drive motors for driving the work device. The drive device comprises a first and a second drive motor, which preferably do not differ from one another in construction or power. One motor is used as the main motor, the second motor can be used as an auxiliary motor, the drive power of the first motor and the second motor being transmitted jointly to the work device by means of a force transmission unit. The use of two drive motors of lesser power instead of one motor of greater power results in a more compact construction of the drive unit, whereby an increase of the power of the drive unit is made possible without exceeding the predefined transport width of the self-propelled construction machine.
Furthermore, the force transmission unit therein comprises a first unit for switching the torque of the first drive motor and/or a second unit for switching the torque of the second drive motor. It is thus possible to selectively engage or disengage the main motor and auxiliary motor as a function of the required power. The transmission of the power from the motors to the work device can be performed via a belt drive or a spur gearing.
Furthermore, a construction machine for processing soil surfaces is known from EP 1 294 991 B1, which comprises an internal combustion engine for the drive of a work roller having replaceable tool elements. The construction machine also comprises an auxiliary drive, which is implemented for the purpose of rotating the work roller around a suitably small rotational angle in the raised state. Tools which have not yet been replaced can thus be moved into a more favorable installation position in order to allow replacement of the tool elements with a reduced need for personnel and time and with a reduced risk of accidents.